In laboratories, it is common practice to use many devices to secure tools in a fixed position. Various types of mechanical clamps, rings, and other grasping implements have been devised to immobilize burettes, funnels, tubes, flasks, and chromatographic columns so they can be used in vertical operation.
A conventional clamping device is disclosed in U.S. Pat. No. 2,269,790. It consists essentially of two functional parts, as do clamping devices generally. One functional part consists of means for grasping the article to be suspended, and the other to affix the vertically held article to a vertical shaft. In '790, both functions are performed by wire bent into the shape of the intended article, and the second by a spring-like wire coil having a bent diameter slightly less than the article, with wire tabs that top of base and top of the coil. Compression of the tabs enlarges the coil diameter permitting insertion of the article. Releasing the tabs compresses the coil against the article, thus firmly folding it in place.
U.S. Pat. No. 1,915,725 discloses a burette holder in which burettes or other cylindrical articles are maintained in position against a frame cavity by applying pressure to opposite side of the cylindrical article with a movable spring-loaded armature. This design allows pressure from one source to impact the cylinder at two or more vertical points on the frame, ensuring vertical disposition of the cylinder. U.S. Pat. No. 2,499,945 discloses a similar apparatus having a single horizontally disposed spring that applies pressure to the cylinder from two such armatures simultaneously. Securing the cylinder-mounting portion of the frame at the ends of the apparatus also provides adequate working space between the cylinder and the support shaft.
The frame is adjustably secured to the support shaft by a vertical collar embracing the shaft and fixed by means of a set screw, which tightens the collar portion to the shaft. This is a common feature of many pieces of laboratory support apparatus, as shown also in U.S. Pat. Nos. 2,269790, 3,893,813, 2,516,965, and 2,499,945. This feature is adequate for laboratory applications because burettes, funnels, and chromatography columns are not heavy objects. However, a set screw is not satisfactory where much weight is involved since there the amount of torque force that can be transmitted by a set screw is limited.
Other types of clamping devices have been disclosed. U.S. Pat. Nos. 2,269790 and 3,893,813 describe grasping apparatus in which both sides of a cylinder are held by separate movable grasping arm. In '813, the apparatus has a frusto-conical adjusting cam wedge such that a spindle knob is helically displaced one way or the other to bear against or retreat from the chambered portions of the arms to open or close a pair of grasping tongs. In '790 clamp arms pivot when a nut is tightened on a threaded portion of a stud, thereby allowing the arms to move towards and away from each other about a common axis.
Finally, U.S. Pat. No. 7,575,676 discloses a square clip device whose interface portion secures the apparatus to a platform, and a second clip device that secures an HPLC column to a correspondingly square shaft. In some embodiments the frictional resistance to displacement of the clip along the shaft is enhanced by placement of upper and lower tooth-like elements which can interact with a securing device having at least one dentated track along its outer surface.